JEE Exam » JEE Study Material » Chemistry »  Law of Thermodynamics

 Law of Thermodynamics

Learn all you need to know about the Law Of Thermodynamics, along with some Law of Thermodynamics questions.

The study of the exchange of energy is known as thermodynamics, as the term thermodynamics in itself denotes that there is some change taking place due to heat. It includes all forms of energy. For example, if we are burning a piece of coal it results in the evolution of heat which makes the entire surroundings warm. So the reaction that took place due to burning coal give out heat, and that heat that was emitted made the surroundings warmer. So the system over here is the area of observation.

What is the meaning of Thermodynamics?

Thermodynamics is an area of physics that helps us comprehend the connection between heat, work, temperature, and the physical properties of energy, radiation, and matter. Here, the conversion of thermal energy into other forms of energy can be understood, and the effect of this process. We also study the thermal effect, where we know the thermal effect produced by microscopic particles during the thermal effect. It also explains the principles of energy transformation, where the change of energy refers to the concept going on between the initial and final states. In this, we read about four laws based on thermodynamics.

What are the laws of thermodynamics? 

  • Zeroth law 
  • First law of thermodynamics 
  • Second  law of thermodynamics 
  • Third  law of thermodynamics 

Zeroth law is the fundamental law, but it came after the first and second laws of thermodynamics. Zeroth law talks about the concept of thermal equilibrium. If two systems are in thermal equilibrium separately from a third system, they must be in thermal equilibrium. For example, if we keep two cups of tea in a small box, now we will add one more cup of tea with a higher temperature. If we check it after a while, the temperature of all the cups will be almost the same.

The 1st law of thermodynamics talks about the conservation of energy, which states that energy cannot be stored, neither can be created nor be destroyed. It can only be converted from one form to another. This law also helps in work transfer and heat transfer. It also states the concept of enthalpy. The 1st law of thermodynamics also gave the concept of internal energy.

The second law of thermodynamics talks about the direction of the flow of heat. The flow of heat is from higher temperature to lower temperature.

Third law of thermodynamics is used to calculate the absolute amplitude of entropies. It states that at absolute zero or 0 Kelvin, a completely flawless or pure) crystalline structure will have no entropy, S. Note that if the structure was not completely crystalline, we couldn’t say it had no entropy because it would only have a very little amount of disorder (entropy) in space.

Before talking about the law of thermodynamics, one should be clear about these terminologies-

System- The system is the part that is under observation. 

Surrounding- The entire part around the system and the remaining part of the universe is called the surrounding. 

Boundary – The surface that will create a diversion between the part under observation and the surrounding is called the boundary.

Applications of the law of thermodynamics 

The law of thermodynamics regulates the functioning of all refrigerators, deep freezers, industrial refrigeration systems, air-conditioning systems, heat pumps, etc. All types of air and gas compressors, blowers, and fans operate on different thermodynamic cycles. This law applies to all types of heat engine cycles, including Otto, Diesel, and many others, and all working fluids used in the engines. This law has resulted in the advancement of modern cars. Light bulbs (radiant energy) convert electrical energy into light energy. When one pool ball collides with another, kinetic energy is transferred, and the second ball moves. Plants transform solar energy (radiant energy) into chemical energy that is stored in organic molecules. Thermal energy is converted into mechanical energy via heat engines and vice versa. The majority of heat engines are classified as open systems. Water is used as the working fluid in a solar-powered air conditioning system. Geothermal Energy Power Generation Using a Closed Thermosyphon Heat Pipe Thermodynamics assists biologists in determining whether biological reactions are viable and the associated energy (or ATP) consumption. It includes metabolic activities, cellular respiration, growth and development processes, membrane transport systems, enzymatic reactions, and many other functions.


Today we are seeing the use of thermodynamics all around, whose special use we also see in our daily lives, the main example of which is tea’s cooling. Apart from this, we see the use of thermodynamics in special places like heat engines, power plants, chemical reactions, refrigerators, which makes us aware of thermodynamics.


Frequently Asked Questions

Get answers to the most common queries related to the JEE Examination Preparation.

Which are the four types of thermodynamic processes?

Ans. Isobaric, isochoric, isothermal, and adiabatic are the four types of thermodynamic processes.

What are the thermodynamic limitations?

Ans. The first law of thermodynamics has a flaw in that it says nothing regarding heat flow direction. It makes no d...Read full

What is the law of thermodynamics?

Ans. The study of the exchange of energy is known as thermodynamics, as the term thermodynamics in itself denotes t...Read full

What is the use of the law of thermodynamics?

Ans. When one pool ball collides with another, kinetic energy is transferred, and the second ball moves. Geothermal ...Read full